1. Technical Field
The present application relates to the field of radio frequency (RF) power dividers and more particularly relates to a class of 2×4 power dividers that produce two pairs of differential unbalanced outputs from two unbalanced inputs.
2. Background
The general input-output relationship of a 2×4 divider, which has two input ports labeled I1 and I2, and four output ports labeled O1, O2, O3, and O4, is shown in FIG. 1. The relative phase of the ports is indicated by FIG. 1 and in the following:
Phase (deg)PortO1O2O3O4I101801800I201800180
In the current state of the art, 2×4 dividers are built using a corporate connection of three 180-degree hybrids as depicted in FIG. 2. The general operation and design of 180-degree hybrids is described in the open literature. See, for example, the IRE Standards on Antennas and Waveguides (1955), Microwave Principles by Reich et al. (1957), Radar Handbook by Skolnik (1990), The RF and Microwave Circuit Design Cookbook by Maas (1998), and “On an Ultrabroad-Band Hybrid Tee” by Barabas (1979), and a few specific designs that are described by U.S. Pat. No. 3,325,587 (1967), U.S. Pat. No. 3,508,171 (1970), and U.S. Pat. No. 5,121,090 (1992).
The corporate arrangement of 180-degree hybrids shown in FIG. 2 requires two interconnecting transmission lines, two resistive loads, and normally requires two impedance transformers to return the impedance to 50-ohms between the hybrids. Such a 2×4 divider can be utilized to generate dual-linear polarization from a four port antenna as depicted by FIGS. 3 and 4. Dual-linear polarized antennas simultaneously support two orthogonal linear polarizations.
Power dividers comprising 180-degree hybrids, resistive loads, and impedance transformers tend to be large, especially at low frequencies; partially due to the fact that 180-degree hybrids are bulky devices. Moreover, such 2×4 dividers have high insertion losses and the two resistive loads do not serve any purpose for applications where the divider feeds into a symmetric device. Hence there is a need to reduce the size and insertion loss of the 2×4 divider by eliminating the interconnecting transmission lines, the resistive loads, and the impedance transformers.